The invention has a broad application in the treatment of a traveling web, but is especially useful in the treatment of a sheet of metal such as steel or aluminum. The term "treatment" as used herein and in the claims, has reference to any process where a continuous web, such as a sheet of metal, paper, film, or textile material, is contacted by a liquid or gas as it moves in a generally horizontal pathway through an enclosed chamber. For example, the treatment of a traveling web includes the electro-galvanizing, de-scaling, or pickling processes of metals, or the cleaning of the web by washing and rinsing, or any other suitable preparation of the web for any subsequent coating, drying saturating, or laminating of the web, or the subsequent operations themselves.
Systems presently on the market for cleaning a sheet of metal or otherwise preparing it for subsequent treatment, such as coating etc., normally employ squeeze rollers between the various treatment tanks for removing excess liquid from the traveling metal sheet so that liquid won't be carried from tank to tank to contaminate or dilute the various liquid solutions being used in the different tanks. However, these rollers become nicked, gouged and otherwise damaged by the sheet of metal to a point where they become ineffective in preventing the traveling metal sheet from carrying liquid between tanks. Such systems also use support rollers that are positioned within the tanks for contacting the traveling metal sheet and guiding it through the bath of liquid used in the treatment of the metal sheet. These support rollers are highly susceptible to rotating slower than the correlated linear speed at which the sheet of metal travels over the rollers to cause slippage between the rollers and sheet of metal and consequent marring of the surfaces of the sheet metal. Thus, the elimination of these two types of rollers would be highly beneficial in the treatment of a sheet of metal.
Sprays are generally used above and below the traveling metal sheet to direct liquid against the adjacent planar surfaces of the metal sheet. The liquid from the sprays contact the metal sheet at angles which are substantially 90.degree. to the plane of the traveling metal sheet. It can be appreciated that the use of such sprays in conjunction with a horizontally traveling metal sheet, generally produces an uneven treatment of the upper and lower surfaces of the traveling metal sheet. For example, a liquid impinged against the top side or upper surface of the metal sheet can form into pools or puddles of liquid which interfere with the impingement upon the surface of liquid from succeeding sprays. In essence, the top side of the metal sheet is usually subjected to a bath or soak process. The opposite is true regarding the processing of the bottom side or lower surface of the traveling metal sheet, where gravity causes the immediate withdrawal of the liquid directed against the bottom side by the sprays located below the traveling metal sheet. In essence, the bottom side of the metal sheet is usually subjected to a spray and drip process. Thus, the opposing surfaces of the traveling metal sheet are exposed to different processing conditions which usually produces non-uniform treatment of the opposing surfaces of the traveling metal sheet.
U.S. Pat. No. 3,328,997 discloses the use of floatation-type nozzles for impinging cleaning liquid against a traveling web. However, the particular apparatus of this patent utilizes in the liquid bath, a number of support rollers which, as previously indicated, can have a deleterious affect upon the treatment of the metal within the bath. The invention is directed to an improved apparatus for the treatment of a traveling web in a liquid bath.
Briefly stated, the invention is in an apparatus used in the treatment of a continuous web or element, such as a sheet of metal, at it travels in a horizontal pathway. The apparatus comprises at least one tank having a horizontally elongated chamber with opposing end walls having horizontally aligned openings through which the traveling metal sheet enters and exits the chamber. Two rows of oppositely disposed, horizontally aligned elongated nozzles, normal to the direction of travel of the metal sheet, are provided in the chamber and positioned to sandwich the traveling metal sheet therebetween. At least one longitudinally extending continuous slot, coextensive with the lateral width of the metal sheet, is provided in the face of each nozzle confronting the traveling metal sheet, and a deflector is provided on each nozzle adjacent the slot for directing a turbulent stream of liquid from the slot angularly against the traveling metal sheet in a direction which is upstream or opposite the direction in which the sheet of metal travels.
A unique liquid seal in the form of a pair of oppositely disposed, similar liquid nozzles, is utilized at the entrance and exit openings of the chamber in combination with air blowoff devices for sealing the openings to prevent the escape of liquid from the chamber into the chamber of an adjacent tank where such liquid could have a harmful affect upon the process being carried on in that particular tank.
Another aspect of the invention is the provision between adjacent nozzles in the chamber of a turbulator which is simply a nozzle that directs a high pressure jet of liquid directly against the traveling metal sheet at an angle of substantially 90.degree., to clash with the highly turbulent flow of liquid produced by the nozzles and create even greater turbulence adjacent the surfaces of the traveling metal sheet.
The successive streams of liquid, as they angularly contact the metal sheet in a counter direction at angles substantially less than 90.degree., provides a unique scrubbing action that is normally not accomplished by the sprays of prior art devices and eliminates the need for auxiliary cleaning equipment, such as scrubbing brushes and other like paraphernalia. The result is an improvement in the quality of the treatment of the metal sheet and consequent reduction in the time required to properly treat the metal sheet.
The liquid seals and blowoff devices eliminate the need for squeeze rollers between adjacent treatment tanks and effectively control the carryover of liquid between adjacent tanks normally experienced when the squeeze rollers become nicked, gouged, or otherwise damaged beyond repair. Consequent contamination or dilution of the liquid of the various treatment tanks is minimized to eliminate the need for frequent replenishment of the liquid and periodic discharge from the tanks of the tainted or weakened liquid which can cause pollution of the drainage system in which such liquid is wasted.
Moreover, the need for guide rollers within the tanks is eliminated because of the liquid beds which are created within the tanks to support the metal sheet. Thus, many of the problems experienced with prior art devices are eliminated, or substantially reduced to where they are inconsequential.